🗃️U3LA3 Mini Project: Card Organizer

How can you use advanced data structures and functional computing with DOM elements and user interaction?

Teacher Notes

Students will be using the concepts from the previous lessons to create a card organizing webpage. Small divs in the shapes of playing cards will be moved from one parent div to another. The medium and spicy extensions introduce new events that javascript can listen for such as: mouseenter, mouseleave, and dblclick.

As students get stuck trying to navigate the DOM tree in search for the right element, continue to encourage them to refer to the actual HTML code both in the index.html and in the devtools on the webpage, and encourage them to constantly use console.log.

Note: This site is not a good example of accessibility, but has been purposely structured for instructional purposes.

Students should utilize the Starter Code (repl.it | github) to begin this project.

Prompt

The holding zone on the website starts with just a couple of playing cards. Can you make it so that the cards can be moved from the holding zone to their matching boxes?

Directions: Write the code for the script.js so that a user can click on a card and click on a box to move the card.

This can be broken down into 2 steps: create an event listener for all the cards on the page, and create one for all the boxes on the page. First, we'll create an event listener for the cards highlighting which has been selected and saving it in a variable. Then, we'll add an event listener to all the boxes that will, on click, "steal" the selected card from the previous box and move it there.

Retrieve all the cards and boxes uses querySelectorAll(), and set up an event listener for each card and for each box. Also, include a variable called selectedCard and set it to null for now. Go try this with your partner before continuing here.

const cards = document.querySelectorAll('button');
const boxes = document.querySelectorAll('.box');

let selectedCard = null;

cards.forEach( card => card.addEventListener('click', () => {
    //
}));

boxes.forEach( box => box.addEventListener('click', () => {
    //
}));

When a card is clicked on, it should "glow" and be saved as the selectedCard. If it is already selected, and is therefore glowing, when it is clicked on, it should stop glowing and the selectedCard variable should be set to null again. The CSS class "is-selected" is already created for you. Try writing this tricky logic on your own before seeing one way to do it below. Here's what it looks like in pseudocode:
- If the card is selected (already)
  - remove the is-selected class from the card and...
  - clear the selectedCard variable setting it to null
- Otherwise (if the card is not already selected)
  - First, Check if there's already a selected card. If there is,
    remove the is-selected class from that card.
  - Then, add the is-selected class to this new card.
  - Finally, make this card the selected card by setting the selectedCard variable to this card

Once you've tried this on your own, this is one way to code it:

cards.forEach( card => card.addEventListener('click', () => {
    if (card === selectedCard) {
        card.classList.remove('is-selected');
        selectedCard = null;
    } else {
        //NOTE: an if statement can be used instead of this ternary
        selectedCard ? selectedCard.classList.remove('is-selected') : {};
        card.classList.add('is-selected');
        selectedCard = card;
    }
}));

See that this feature works on the website. You should now be able to click and un-click cards. Add a console.log(selectedCard) if you'd also like to see that that variable is tracking properly.

Now, set up the boxes. First, we only want a click event to happen if there is a selected card and if the box we click is a different box then the one the card is coming from. Use parentElement to find the box that belongs to the clicked card. Then set up the if statement as follows:
```
boxes.forEach( box => box.addEventListener('click', () => {
    if(selectedCard && box !== selectedCard.parentElement.parentElement) {
        console.log("available box");
    }
}));
```
When an available box is clicked, we want to do 4 things:
- Remove the card from the box it came from
- Add the card to this box
- Remove the is-selected class from the card
- Clear the current selectedCard *See how far you can get with these on your own before reading on.

To remove the selected card from the box it came from, use parentElement to get the element it's currently in and removeChild() to remove it.

boxes.forEach( box => box.addEventListener('click', () => {
    if(selectedCard && box !== selectedCard.parentElement.parentElement) {
        // Remove the card from the box it came from
        selectedCard.parentElement.removeChild(selectedCard);
    }
}));

We're going to use appendChild() to the box, but first we need to find the right element. For now, log the box.childNodes and check the console. This will output an array of all the child nodes that belong to the box. Index the element "div.cards", and append the selectedCard to it.

boxes.forEach( box => box.addEventListener('click', () => {
    if(selectedCard && box !== selectedCard.parentElement.parentElement) {
        // Remove the card from the box it came from
        selectedCard.parentElement.removeChild(selectedCard);
        // Add the card to this box
        box.childNodes[3].appendChild(selectedCard);
    }
}));

Last, remove the is-selected class from the card and clear the current selectedCard.

boxes.forEach( box => box.addEventListener('click', () => {
    if(selectedCard && box !== selectedCard.parentElement.parentElement) {
        // Remove the card from the box it came from
        selectedCard.parentElement.removeChild(selectedCard);
        // Add the card to this box
        box.childNodes[3].appendChild(selectedCard);
        // Remove the `is-selected` class from the card
        selectedCard.classList.remove('is-selected');
        // Clear the current selectedCard
        selectedCard = null;
    }
}));

Exemplar

Take a look at this finished example (repl.it | github) for the finished version of the site.

Culturally Responsive Best Practice

Students may be color blind, or may not have any experience with playing cards and their suits. This lab doesn't require prior experience with a deck of cards, and the suits' shapes are distinct enough to distinguish regardless of visual deficiencies. However, consider having students play a couple of matching games with a deck of cards to become more familiar and comfortable with the idea.

Extra Help?

Check out these other events that can be listened to: mouseleave, mouseenter, and dblclick.
Another resource for createElement() which is used to create customized HTML before adding it to the page.
Not understanding DOM traversal (parent, child, grandparent nodes)? Check out this video resource on some more examples.
Need a video resource on adding and removing elements, attributes, and classes? Check the timestamps for this video resource.

Extensions

Mild

Add 2 more cards of your choice. Ensure that all the functionality still works.
Add a 5th suit. Use whichever symbol you'd like. Add a card with that same suit and be sure that you can move the card to that new box.

Medium

Create a checkBoxes() function that checks if all the cards are sorted properly. The function should be called after every card is moved. If everything is sorted, display a message or an alert saying so.
Go to randomCards.js and notice that there is a function that returns an array of random cards from an array of all possible cards called getRandomCards(). Change the code so that these random cards are the cards that first appear on the screen in the holding zone.
Highlight an available box when the mouse hovers over it. Add a mouseenter and mouseleave event listener to the boxes. The is-selected class should be added when a mouseenter happens, and it should be removed when the mouseleave happens or when a box is selected. NOTE: this effect should only happen if a card is selected, and if the hovered box is not the box of the selected card.

Spicy

Change the code so that multiple cards can be selected at once before moving them to a new box.
Add an on "double click" event (dblclick) to the holding zone box so that when a user double-clicks that box, a new card appears.
Use local storage to save the last state of the card organizer upon refresh of the page. Check out this resource on local storage to learn more.

Reflection Questions:

What are you most proud of? What did you struggle the most with?
With more time what would you have liked to add to the page?
What's one thing you liked about having a partner for this lab?

PreviousU3LA3.2: Advanced DOM Manipulation NextU3LA4: Local Storage

Last updated 10 months ago